1. Field
This invention relates to the field of digital image processing, in particular the design and optimization of Color Filter Arrays for CMOS image sensors.
2. Related Art
To the average consumer of digital imaging products, the pixel count, or the number of ‘mega pixels’, is synonymous with image quality. Consequently, there is a trend amongst consumers to buy the digital imaging device that advertises the largest pixel count in their price range. As a result of this positive feedback, sensor manufactures are fiercely competing to roll out larger and larger format sensors with ever shrinking pixel size. Shrinking sensor pixel size, however, poses significant challenges to sensor design.
As pixels size decreases, the pixel crosstalk inevitably increases. Crosstalk describes the phenomena in which photons falling on one pixel are “falsely” sensed by surrounding pixels. For example, crosstalk occurs when highly focused light is directed to hit only a red colored pixel, yet the surrounding green and blue colored pixels show a response as demonstrated in FIG. 1. In this extreme case, the green channel response will be too high and skew the real pixel color. It is commonly understood that the crosstalk degrades the spatial resolution, reduces overall sensitivity, causes color signal mixing and, consequently, leads to image error after color correction. Reducing the effect of crosstalk in small pixels, therefore, has become one of the major goals in CMOS image sensor design.
Hence there is a need for a method in color filter design to compensate for the crosstalk in color imaging at the system level. Part of this method is a color reproduction model for CMOS and CCD image sensor under the effect of pixel crosstalk.